Science / Technology - Colloquium
Monday, February 20, 2006
4:00 PM-5:00 PM
Olin Hall
107
The diffusion of matter from one region into another is a universal phenomenon occurring in gases, liquids and solids. In metallic alloys, we can study diffusion by putting two alloys together and allowing the components of one alloy to diffuse into the other alloy at high temperature, and then quenching the system to freeze the diffusion. We can then experimentally determine the concentration profiles. Such diffusion under controlled conditions gives us information about the diffusion process and the stability of the interface. This has wide applications in the welding of metals and similar industrial processes.
Until recently, the diffusion coefficients could not be determined in a reliable manner in multicomponent diffusion, such as ternary or quaternary diffusion. They are functions of composition, making diffusion an intrinsically nonlinear process. I will present a new method of determining the diffusion coefficients developed recently, and show how the concentration profiles can be reconstructed, given the diffusion coefficients, using a transfer-matrix method (TMM). The TMM developed by me is applicable to any number of diffusion components.
I will also mention the directions in research we are pursuing. We are close to being able to predict the diffusion path in a diffusion couple given the end compositions. Diffusion in three- and four-component systems already displays a rich variety of complex phenomena. I will illustrate these with examples. We are starting on an investigation of grain boundary diffusion and triple junction diffusion in macroscopic and nanoscopic systems.
Undergraduate and graduate students are encouraged to attend.
Cost: FREE
Sponsored by: WPI Physics Department, Dr. Rafael Garcia
Suggested Audiences: College
E-mail:
garcia@wpi.edu
Phone: 508-831-5342
Last Modified: February 3, 2006 at 9:57 AM
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